Oxidation of mercaptans



No Drawing. Application June so, 1952',

. Serial No.296,477

18 Claims. c1. 196-29 This invention relates to the oxidation of mercaptans 'and more particularly to etfecting this reaction in the presence ofa particular class of compounds.

' As is well-known, mercaptans are contained in various hydrocarbon fractions, including liquid fractions such as gasoline,kerosene, gas oil, diesel oil, heater oil, range oil, etc., as well as being contained in normally gaseous hydrocarbon fractions. The presence of mercaptans is objectionable in these fractions for a number of reasons, including undesirable odor, corrosiveness, etc.

In one embodiment the present invention relates to a method of oxidizing a mercaptan to a disulfide which comprises reacting the mercaptan with an oxidizing agent in the presence of'an organo-metalliccompound.

In a specific embodiment the present invention relates to a method of oxidizing a mercaptan contained in gasoline which comprises reacting said mercaptan with oxygen in the presence of a basic reagent and an organo-metallic compound. 7

As hereinbefore set forth the mercaptans generally will be contained in a hydrocarbon fraction and usually will be present in asmall concentration.- --When the original mercaptan content of the hydrocarbon fraction is substantial, it generally is preferred to. treat the hydrocarbon fraction-by means of a suitable alkaline material, including'sodium hydroxide, potassium hydroxide, etc., with or without a solutizer, includingphenols, cresols, xylenols, isobutyric acid and salts thereof, alcohols and particularly methanol, etc., in order to remove a major proportion of the mercaptans. However, it generally is diflicult to remove thefinal traces of mercaptans; and the present-in- United States Patentbf vention is of particular advantage to convert the. remain- I ingmercaptans into disulfides and therebyto produce'a sweethydrocarbon fraction. v

Air or'other suitable source of oxygen is present in order't'o eflfect oxidation of the mercaptans to disulfides. In some cases air dissolved or entrained in the hydrocarbon fraction will be suflicient to effect the'desired oxidation. In other cases it may be preferred to introduce air from an extraneous source, particularly when the distillate'is'storedin-tanks having floating roofs which serve to exclude air. While air'is preferred, it is understood that other suitable oxidizing agents may be employed including oxygen, ozone, hydrogen peroxide, etc.

' The oxidation of mercaptans is generally facilitated by the presence of a basic reagent and, in a preferred embodiment of the invention, the oxidation is eifected in the presence of a. basic reagent. Any suitable basic reagent may be employed. The basic reagent may be inorganicand include sodium hydroxide, potassium hydroxide, etc., or these reagents containing a solutizer as hereinbefore setforth. In some cases the pretreatment of the hydrocarbon fraction with the basic reagent will leave a small amount of basic reagent entrained in the gasoline, and the small amount may be suflicient for the present purpose. In addition to or in the place of the inorganicj bas'ic reagents, suitable organicv basic reagents may be employed including,"for example, heterocyclic 2,744,854 Patented; May 8, 1956 "ice.

nitrogen compounds suchas pyridine, pipei'idine, picoline, lutidine, quinoline, pyrrole, pyrazole, indol, carbazole, acridine, etc., quaternary'ammoniumcompounds including tetraalkyl ammonium compounds, and'particw larly tetrabutyl ammonium hydroxide, tetraamylammo-z nium hydroxide, etc., tetrapropyl ammonium methoxide, tetrabutyl ammonium methoxide, tetraamyl ammonium methoxide, etc., tetraethyl ammonium ethoxide,- tetra propyl ammonium ethoxide, tetramethyl ammonium propoxide, tetraethyl ammonium propoxide, tetrapropyl am= monium propoxide, etc., and" similar tetra-substituted ammonium pentoxides, 'hexoxides, heptoxides, octoxides, etc., as well as benzyl trialkyl ammonium hydroxidesand alkyl oxides, etc. Other organic basic compounds in clude the aliphatic amines such as propyl amine, butyl' amine, amyl amine, etc., dimethyl amine, diethyl amine, dipropyl amine, etc., trimethyl amine, triethyllamin'e, tripropyl amine, etc., trimethylene'diamine, tetramethylene diamine, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentainine, etc. It is understood that mixtures of the inorganic basicreagents, 'mix tures of the organic basic compound, and/orrnixtures of the organic basic reagent or reagents and mixtures of the organic basic compound or compounds may beem'ployedfi It generally is preferable to also utilizeia' phenylene" diamine' compound and particularly anN,N -dia1kyl-pphenylene diamine which has been found tdfailitate oxidation of mercaptans to disulfides. Of the ph'enylene diamines, N,N"-di;secondary-butyl-p phenylene 'diamitie is preferred. Other suitable phenylenfe diaminecompounds include N,N-di-isopropylp-phenylene'"diaminef N,N'-di secondary-amyl-p-phenylene diamine, N-isopro pyl N' secondary butyl-p phenylene diamine, N- isop'ro'-' pyl-N' secondary-amyl-p-phenylene "diamine, N-sec'ond ary-butyl N'-secondary-amyl-p-phenylene diamine, etc. It is understood thatothersubstituted phenylene diamines in' which one" or more 'alkyl' radicals are substituted an the amino'hydrogens or are attachedto the phenyl ringsQ these alkyl radicals being the same or difieren't, are' coir'i prised withinthe scope-of the present invention humor necessarily with equivalent'resultsi' The phenyl ene mine compound generallywillbe used-in'aconcentration of from about 0.00o1-%'ro about 015 byw'eightl of the hydrocarbon fraction and preferably of from a out 0.0005% to about 0.05% by weight. In accordance with the present invention, oxidation or mercaptans tod'isulfidesis etfectedjin the presence ofa'n organo-metallic compound. The ,organo metallic compound may comprise any suitable hydrocarbon solublef organo-metallic compound. Preferred metals comprise? cobalt, chromium, copper, iron, manganese, -nickel*and vanadium. These metals may beutilize'd as salts of high molecular Weight organic acids including the 'palmitates," stearates,'oleat'es, naphthenates, etc. In another embodiment the organo-metallic compound may comprise a chelated compound, including the meet chelates of the condensation product of an orthohydroxy aromatic compound with a suitable nitrogen compound. The ortho-hyd'roxyaromatic aldehyde may be's'ubstituted with alkyl, nitrogen, sulfur, oxygen, halogen, alkyl I, groups containing nitrogen, sulfur or oxygen,- orfnixcompounds include metal chelatesof the condensation product of salicylaldehyde with an o-aminophenol. Still other satisfactory compounds comprise. ortho-hydroxyaromatic oxines, including salicylaldoxine, etc., thetetra metal salts of ethylene diamine tetraacetic acid and. simi lar compounds.

Other satisfactory chelated' ing butyl mercaptan, piperidine and N,N'-di-secondarybutyl-p-phenylene diamine, the addition of iron oleate in a concentration of 1 milligram of metal per liter of gasoline reduced the mercaptan content to 0.00029% b weight.

Example V Example VI The gasoline used in this example was a Mid-Continent thermally cracked gasoline which had been caustic treated to reduce the mercaptan content to substantially zero. 0.01% by weight of mercaptan as normal butyl mercaptan, 0.01% by weight of N,N'-di-secondary-butyl-p-phenylene diamine and 0.0001 gram of the cobalt chelate oi disalicylal propylene diamine per 400 grams of gasoline were added. After 19 hours in storage, the mercaptan content was reduced to zero and the peroxide number was only 0.015.

I claim as my invention:

1. A method of oxidizing a mercaptan which comprises reacting the mercaptan with an oxidizing agent in the presence of a metal chelate and a phenylene diamine.

2. A method of oxidizing a mercaptan to a disulfide which comprises reacting the mercaptan with oxygen in the presence of a metal chelate and a phenylene diamine.

3. The process of claim 2 further characterized in that the metal of said chelate is selected from the group con sisting of cobalt, iron, manganese, copper, nickel, vanadium and chromium.

4. The process of claim 3 further characterized in that said metal is manganese.

5. The process of claim 3 further characterized in that said metal is copper.

6. The process of claim 3 further characterized in that said metal is cobalt.

7. The process of claim 2 further characterized in that the metal compound is a chelate of a disalicylal polyamine alkane.

8. The process of claim 7 wherein said disalicylal polyamine alkane comprises disalicylal diamino propane.

9. A method of oxidizing a mercaptan contained in a hydrocarbon fraction which comprises reacting said mercaptan with oxygen in the presence of a metal chelate and a phenylene diamine.

10. A method of oxidizing a mercaptan contained in gasoline which comprises reacting said mercaptan with air in the presence of a basic reagent, a metal chelate and a phenylene diamine.

11. The process of oxidizing a mercaptain contained in gasoline which comprises reacting said mercaptan with air in the presence of a basic reagent, a phenylene diamine and a chelate of a disalicylal polyamine alkane and a metal selected from the group consisting of cobalt, iron, manganese, copper, nickel, vanadium and chromium.

12. The process of claim 11 further characterized in that said basic reagent comprises caustic.

13. A method of oxidizing a mercaptan contained in gasoline which comprises reacting said mercaptan with air in the presence of caustic, a phenylene diamine and a cobalt chelate of disalicylal diamino propane.

14. A method of oxidizing a mercaptan contained in gasoline which comprises reacting said mercaptan with air in the presence of caustic, a phenylene diamine and a manganese chelate of disalicylal diamino propane. 1

15. A method of oxidizing a mercaptan contained in gasoline which comprises reacting said mercaptan with air in the presence of caustic, a phenylene diamine and a copper chelate of disalicylal diamino propane.

16. A process which comprises treating a hydrocarbon fraction containing mercaptans with a basic reagent to remove a substantial portion of the mercaptans, and thereafter treating the gasoline with oxygen in the presence of a metal chelate and a phenylene diamine.

17. A process which comprises treating gasoline containing mercaptans with a caustic solution to remove a substantial proportion of the mercaptans, and thereafter treating the gasoline with air in the presence of a metal chelate of disalicylal diamino propane, caustic and an N,N-dialkyl-p-phenylene diamine.

18. The process of claim 17 further characterized in that said N,N'-dialkyl-p-phenylene diamine comprises 7 N,N-di-secondary-butyl-p-pheny1ene diamine.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF OXIDIZING A MERCAPTAN WHICH COMPRISES REACTING THE MERCAPTAN WITH A OXIDIZING AGENT IN THE PRESENCE OF A METAL CHELATE AND A PHENYLENE DIAMINE. 